A conventionally known turbocharger includes a turbine, a wastegate passage that bypasses the turbine, and a wastegate valve arranged in the wastegate passage. The wastegate valve opens the wastegate passage to reduce exhaust gas flowing into the turbine when the pressure of the exhaust gas exceeds a predetermined value.
A known example of a technique for detecting a fault of a wastegate valve is determining whether a detection value of a boost pressure exceeds a limit and indicating a fault when the detection value exceeds the limit (e.g., refer to Patent Document 1).